The present invention relates to fuser members and to processes for providing elastomer surfaces on a substrate. More specifically, the present invention relates to members comprised of a substrate and thereover a crosslinked latex fluoroelastomer surface in which members can be selected for a supporting substrate useful in electrostatographic processes, inclusive of digital processes and devices. The present invention provides an environmentally friendly fluorocarbon elastomer surface for a fuser system member with the positive features of having chemical, physical and thermal stability, along with sufficient toughness to resist wear and tear.
The invention dispenses with the additional costs associated with materials such as organic solvents and further, dispenses with the need for their disposal. This helps prevent air pollution and provides an environmentally friendly latex fluorocarbon elastomer emulsion. In addition, the present invention minimizes the need for functional fusing oils which are normally necessary to prevent toner from adhering to the surface of the fuser member. Nonfunctional fuser oils would be preferred due to economic considerations. Moreover, the present invention provides a fusing system member which has sufficient toughness, along with excellent chemical, physical and thermal stability, and other properties allowing for a larger fusing latitude at higher temperatures (400-450xc2x0 F.) and decrease in the problems associated with hot offset.
In a typical electrostatographic reproducing apparatus, a light image of an original to be copied is recorded in the form of an electrostatic latent image upon a photosensitive member and the latent image is subsequently rendered visible by the application of electroscopic thermoplastic resin particles which are commonly referred to as toner. The visible toner image is then in a loose powdered form and can be easily disturbed or destroyed. The toner image is usually fixed or fused upon a support, which may be the photosensitive member itself or another support sheet such as plain paper.
Thermal energy is commonly used for fixing toner images onto a support member. To fuse electroscopic toner material onto a support surface permanently by heat, it is usually necessary to elevate the temperature of the toner material to a point at which the constituents of the toner material coalesce and become tacky. This heating causes the toner to flow to some extent into the fibers or pores of the support member. Thereafter, as the toner material cools and solidifies, it becomes firmly bonded to the support.
Typically, the thermoplastic resin particles are fused to the substrate by heating to a temperature of between about 90xc2x0 C. to about 200xc2x0 C. or higher depending upon the softening range of the particular resin used in the toner. It is undesirable, however, to increase the temperature of the substrate substantially higher than about 250xc2x0 C. because of the tendency of the substrate to discolor or to catch fire at such elevated temperatures, particularly when the substrate is paper.
Several approaches for accomplishing thermal fusing of electroscopic toner images have been described. These methods include providing the application of heat and pressure substantially concurrently by various means, such as by a roll pair maintained in pressure contact, a belt member in pressure contact with a roll, and other equivalent means recognized in the art. Heat may be applied by heating one or both of the rolls, the plate members or belt members. Fusing of the toner particles takes place when the proper combination of heat, pressure and contact time is provided. Various strategies for balancing these parameters to bring about the fusing of the toner particles have been described in the art, and it is recognized that the parameters can be adjusted to suit particular machines or process conditions.
During operation of a fusing system in which heat is applied to cause thermal fusing of the toner particles onto a support, both the toner image and the support are passed through a nip formed between the roll pair, or plate or belt members. The concurrent transfer of heat and the application of pressure in the nip affects the fusing of the toner image onto the support. It is important in the fusing process that no offset of the toner particles from the support to the fuser member take place during normal operations. Toner particles offset onto the fuser member may subsequently transfer to other parts of the machine or onto the support in subsequent copying cycles, thus increasing the background or interfering with the material being copied there. The referred to xe2x80x9chot offsetxe2x80x9d occurs when the temperature of the toner is increased to a point where the toner particles liquefy and a splitting of the molten toner takes place during the fusing operation with a portion remaining on the fuser member. The hot offset temperature or degradation of the hot offset temperature is a measure of the release property of the fuser roll, and accordingly, fusing surfaces with a low surface energy which provide the necessary release are desirable. To ensure and maintain good release properties of the fuser roll, it has become customary to apply release agents to the fuser roll during the fusing operation. Typically, these materials are applied as thin films of, for example, silicone oils, to prevent toner offset.
Particularly preferred fusing systems are comprised of a heated cylindrical fuser roll having a fusing surface that is backed by a cylindrical pressure roll forming a fusing nip there-between. A release agent donor roll is also provided to deliver release agent to the fuser roll. While the physical and performance characteristics of each of these rolls, and particularly of their functional surfaces, are not precisely the same because of the various characteristics of the fusing system desired, the same classes of materials are typically used for one or more of the rolls in a fusing system in an electrostatographic printing system.
In U.S. Pat. No. 5,736,250, the disclosure of which is incorporated by reference in its entirety, there is described crosslinked fluorocarbon elastomer surfaces comprising a fluorocarbon elastomer and an amino siloxane and a method for providing a crosslinked fluorocarbon elastomer surface on a fuser member supporting substrate which includes mixing together an acid acceptor, an emulsifier, water, and amino siloxane with a latex fluorocarbon elastomer.
In U.S. Pat. No. 5,166,031, the disclosure of which is incorporated by reference in its entirety, there is illustrated a fuser member comprising a supporting substrate having an outer layer of a volume grafted elastomer which is a substantially uniform integral interpenetrating network of a hybrid composition of a fluoroelastomer and a polyorganosiloxane, the volume graft having been formed by dehydrofluorination of a fluoroelastomer by a nucleophilic dehydrofluorinating agent, followed by addition polymerization by the addition of an alkene or alkyne functionally terminated polyorganosiloxane and a polymerization initiator, and wherein the fluoroelastomer can be selected from a group consisting of poly(-vinylidene fluoride-hexafluoropropylene) and poly(vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene).
U.S. Pat. No. 5,366,772, the disclosure of which is incorporated by reference in its entirety, describes an outer layer of a fuser member comprised of a substantially uniform integral interpenetrating hybrid polymeric network comprised of a haloelastomer, a coupling agent, a functional polyorganosiloxane and a crosslinking agent. The hybrid polymeric network is formed by the sequential reaction of the haloelastomer with a dehydrohalogenating agent, reaction with the coupling agent, condensation with the functional polyorganosiloxane and crosslinking with the crosslinking agent.
U.S. Pat. No. 5,370,931, the disclosure of which is incorporated by reference in its entirety, describes a grafted elastomer which is a substantially uniform integral interpenetrating network of a hybrid composition of a fluoroelastomer and a polyorganosiloxane, said graft having been formed by dehydrofluorination of said fluoroelastomer by a nucleophilic dehydrofluorinating agent, followed by addition polymerization by the addition of an alkene or alkyne functionally terminated polyorganosiloxane and a polymerization initiator; and wherein said outer layer contains copper oxide in an amount of from about 2 to about 7 weight percent based upon the total weight of said outer layer.
U.S. Pat. No. 5,456,987, the disclosure of which is incorporated by reference in its entirety, describes an intermediate transfer member having a layer comprised of a grafted titamer formed using a coupler having at least one pendant silane group.
U.S. Pat. No. 5,337,129, the disclosure of which is incorporated by reference in its entirety, describes an intermediate transfer member comprising a substrate and a coating comprised of integral, interpenetrating networks of haloelastomer, silicon dioxide and optionally polyorganosiloxane coupled using an amine coupler having at least one pendant functional group such as silane.
U.S. Pat. No. 4,399,553, the disclosure of which is incorporated by reference in its entirety, describes a water-based fluoroelastomer coating composition comprising a fluoroelastomer and an amino silane.
There is also known a water-based fluoroelastomer coating composition comprising an aqueous fluoroelastomer dispersion blended with a polyamine compound (e.g., hexamethylenediamine carbamate, N,N-dicynnamylidene-1,6-hexanediamine) as a vulcanizing agent (cf. DuPont""s xe2x80x9cViton,xe2x80x9d Bulletin, No. 5, April, 1961).
Currently, fluorocarbon elastomer substrates have been applied as a thin layer to surfaces using an organic solvent spray or other liquid organic process.
Normally, the fluorocarbon elastomer is first dissolved in volatile organic solvents, such as acetone, methyl ethyl ketone, methyl isobutyl ketone and the like, to facilitate the deposition of the thin films of fluoroelastomer on the substrates to be coated and to enable the solvent to evaporate into the atmosphere within a reasonable period of time. The use of such volatile organic solvents as diluents can result in air pollution.
The drawbacks of using organic solvents or other liquid organic processes to coat surfaces with fluoroelastomers includes the high cost relative to other coating processes that contain water as the primary solvent or diluent, associated with the organic solvent and the attendant vapor filters. In addition, as the concern over hydrocarbon air pollution by state and federal governmental agencies and private interest groups increases, and as environmental and health regulations on air pollution resulting from volatile organic solvents tighten over time, a need exists for fuser containing fluoroelastomers on surfaces that do not result in excessive volatile organic solvent emission. Further, a need exists for the generation of fluoroelastomers such as the environmentally friendly fluoroelastomers described, wherein these fluoroelastomers have the desirable properties necessary for a surface for a fusing system member, including high toughness, along with excellent chemical, physical and thermal stability, and properties allowing for a decrease in the problems associated with hot offset. In addition, there exists a need for a fuser surface which minimizes the necessity for use of a release agent. These and other needs can be achieved with the present embodiments thereof.